Field of the Invention
This invention concerns casing methods, and more particularly a method of creating an open riser in a mold during casing.
Description of the Prior Art
Molds often incorporate one or more "riser" passages extending vertically up from a mold cavity, allowing liquid metal to rise within the riser passage when molten metal is poured into the cavity through a down sprue. The purpose of the metal in riser is to prevent shrinkage from occurring during solidification by allowing shrinkage to be made up by met from the riser.
Insulating and exothermic riser sleeves are often used to keep the metal in the riser liquid to allow a shrinkage make up flow of metal back into the mold cavity.
Blind risers are those riser passages which do not open to outside of the mold, and these have sometimes been formed by burying a polystyrene similar heat consumable material mass in mold sand which gasifies upon contact with the hot metal to allow the metal to rise into the blind riser.
See for examples U.S. Pat. No. 3,602,292 issued on Aug. 31, 1971 for "Casing Molds Having Decomposable Hollow Risers"; U.S. Pat. No. 4,140,838 issued on Feb. 20, 1979 for "Sand Mold Risers"; and U.S. Pat. No. 5,271,451 issued on Dec. 21, 1993 for a "Metal Casing Using a Mold Having Attached Risers".
It sometimes is desirable to have an "open" riser which extends to the outside of the mold so that additional metal can be poured into a riser as needed to insure that shrinkage completely made up.
However, when a mold is being made by an automatic matchplate molding machine or a cope and drag type molding machine the squeezing of the mold sand makes it impossible to form the open riser without the possibility of dislodging mold sand which can then drop into the mold cavity as the squeeze process proceeds.
A manual or separate automatic cutting operation is also required.
It is the object of the present invention to provide a method of forming an open riser passage in a mold which is constructed by a process including a mold sand squeezing operation.